


What Friends Are For

by gisho



Category: Girl Genius
Genre: Friends With Benefits, Mid-Canon, Threesome, the amazing falling machine
Language: English
Status: Completed
Published: 2019-05-03
Updated: 2019-05-03
Packaged: 2020-02-16 10:59:08
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,831
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18690136
Author URL: https://archiveofourown.org/users/gisho/pseuds/gisho
Summary: Gil invites his old friends to have some fun, now that they're all on speaking terms again. And when the flying machine gets back, they invite him to bed, to his confusion.





	What Friends Are For

\--

Gil takes a deep breath. They're his friends, he reminds himself. He trusts them. He used to tag along with Theo and Sleipnir while they snuck into the Large Mechanical Labs, standing pressed so close between them on the lighting platform he could feel Theo's gasp when the latest giant clank unfolded. This isn't really that different, Gil tells himself, even after four years without so much as a letter. 

"Hey," Sleipnir says, and lays a hand on his shoulder. "We don't have to. It was Theo's idea, not yours. If you'd rather just -"

"No!" Gil finds himself frantically waving his hands. "No, it's fine, this is fine."

Theo puts in, "Are you sure? You're acting all - " He makes one of those hand gestures that really only means something in context, full of abstract circles and wiggling fingers. It probably translates as _idiotic_. Gil certainly feels idiotic right now. There are times Gil wonders how most people get through the day without accidentally setting themselves on fire, and there are times he suspects it's because they've dedicated so much of their brains to reading each other's facial expressions and picking out the perfect things to say, and Gil isn't completely sure that he got the better trade. 

Mostly sure, though. 

He looks at the closed door and takes another breath; extra oxygen is good for cognition. "Yes." The door isn't locked, and Gil gives up fiddling with the top button of his shirt and goes to shut it. They don't want anyone barging in on them.

Theo's already turned away, and he's scrambling down the stairs. "It's beautiful," he says, not that it's really visible in the moonlight. Turning the lights on would just attract attention. "How did you get the wings to fold like that?"

"I'll show you." He follows, trying to move fast enough that Sleipnir doesn't bowl him over, and vaults into the pilot's seat. The wing-extension lever is right there and he grabs for it before Theo can try, and the wings spring wide open. 

There's barely room for them in here. They stretch all the way out to the lab walkways, where they'd catch if he tried to open the floor. 

"Oooh." Sleipnir's hand tightens on his shoulder, and Gil realizes with a guilty start that he could have knocked her over with the wing. Except she can take care of herself, obviously. "Bipneumatic actuators?"

"Saves power." They retract a little reluctantly, as always, like they don't want to give up the air.

"It's a beautiful piece of engineering." Theo sounds a little breathless. "Did you get it repaired enough to fly?"

"I did. Uh. It's not really built for three ..." He looks over his shoulder. Sleipnir is perched in Theo's lap, his arms firmly wrapped around her and his chin on her shoulder. They're both grinning. "But it can take the weight. Hold on tight." He pulls the door release.

The bay floor slams open and the flying machine drops into the night.

Someone is whooping with delight. Gil hopes it isn't him. He counts five-and-a-half seconds through the weightless joy while they plummet past the support fleet, its lights too yellow and moving too fast to be mistaken for stars, then grabs the wing control again. They fling themselves open and the flying machine catches on the air as he slams the starter button. The engine roars to life.

His passengers whoop in unison, barely audible over the roar of the engine. Gil laughs as he twists at the throttle, and they're suddenly swooping away, throwing themselves through the night with wild abandon. Thank you, Miss Clay, his top speed's gone up fifteen percent. 

Flying at night, the view isn't as splendid. The Wastelands are a shapeless black void far below them, horizon to horizon, not a town in view even from this height. The sky is more interesting, wispy high-altitude clouds to the north and clear skies to the south. The arc of the Milky Way is easy to steer by. Gil yanks back on the wing controls. They pull up into a level glide, headed away from Castle Wulfenbach too fast for anyone to catch. [1]

[1]The top speed of Castle Wulfenbach was a state secret, and Gil hadn't worked out it was seventeen kilometers an hour until he was ten, but everyone knew the message coracles topped out at fifty-seven. 

\--

The hills that were on the western horizon have vanished beneath them, and the dim fires of a walled village are just visible where they separate from the stars, before Theo speaks. "I see why you like this thing," he says, just loud enough to make out over the purr of the engine.

Sleipnir is laughing. "How far could we go?"

"Maybe two hundred kilometers, I haven't run tests with the new fuel additive!" He doesn't need to yell, really, not with the engine steady, but Gil can't resist it. "Isn't Miss Clay wonderful?"

He can't see Sleipnir's grin, but he doesn't have to. "We could go all the way to Budapest! Want to run away with us?"

"Weren't you listening?" Theo puts in. "We'd have to go back for Miss Clay."

At least they can't see him blushing. "We'd have to go back for Zoing," he corrects them, like he hadn't abandoned his friend for four years to go to Paris. 

"He'd survive a week without you."

Oh. A week. They hadn't meant - Gil tries not to feel disappointed. He wouldn't want to be the third wheel when they elope. He couldn't have said yes, anyway, if he tried to vanish for good his father would have him dragged home by his earlobes. A week's holiday he might overlook.

Might. Or he might consider it failing another test.

"If you want to go I'll show you how to fly this thing," he says. "I have to be home by morning, though."

For a few seconds he think he's said something wrong. Then Sleipnir's breath is warm in his ear again, as she says, "Show us."

\--

It makes something in his chest go tight and painful to make the turn, even knowing he's used up almost half the fuel he made this afternoon, even with Castle Wulfenbach invisible over the horizon. Gil swallows the feeling, knowing it's irrational. 

Behind him Sleipnir and Theo have gone quiet. Still absorbing the flying lessons, maybe. He'd taught them how to adjust the tail, how to balance the wing area to dip and turn, exactly how far you could turn to the side without falling out and how slow you could go without making the engine sputter out. This wasn't an airship, after all. You had to keep moving, like a bird. Gil would miss it if they eloped in it.

Well, he can always build another. There's that helicoil fall arrestor he's been meaning to try.

When the Castle comes in sight again it's obvious from how far below it is, the only patch of light against the roiling darkness of the Wastelands. Gil squints at the yellow beacons of the support fleet. He can see a coracle moving away, taking some urgent message or ferrying an important passenger, but at this hour of the night there's no arriving cargo, no crises driving the military fleet to a frenzy. They'll be seen coming in, of course. That's fine. The picket fleet know the flying machines are just a madboy's toys, no threat to Castle Wulfenbach.

Sleipnir gasps, and her arms tighten on Gil's ribs. "We must be a kilometer up."

"Just about. I've never hit the flight ceiling on this thing." Gil grins and his hand tightens on the angle lever. He shouldn't try right now, not with passengers. 

"Maybe next time. I'll bring pneuma masks. Would you believe they still haven't changed the door codes on Medical Bay Seventeen?"

"I mean," Theo puts in, "we're not complaining! We'd never have gotten that centrifuge working if they did! How does this thing land? Are we going to hit the greenhouses?"

What centrifuge? What have they been doing for - four years he wasn't with them? Gil twists left and the machine is suddenly pointing due east, not quite toward Castle Wulfenbach anymore. "The flight lab has retracting windows," he calls back. "Timing is a little tricky, that's all."

"Well, you can't do worse than this morning!" 

Traitors. He'd spent all afternoon rebuilding his flying machine and adjusting the engine for its new fuel mixture, and they were going to mock him for getting a little distracted. Gil grins, and yanks back the wing-control knob.

The wings fold in and they drop like a rock.

Behind him Sleipnir and Theo are shrieking. It sounds a little more like glee than laughter, but it's hard to tell over the whistling wind and his own maniacal laughter. Somehow everything sounds louder in the dark.

Gil waits until they're level with the Castle to let the wings unfold again. They swoop up, and level out into an even glide almost at once. The screaming takes longer to die down. Gil forces a few deep breaths, overriding the urge to giggle. "I know a few tricks," he yells instead.

"We can tell!" Sleipnir's arms go tight for a second and then let go, like she's trying for a comforting hug.

Theo puts in, "Can you make it do a backflip?"

"No." Not with the wing structure he has now, not if he doesn't want them ripped off by the strain. But maybe, with aluminium reinforcements - "Not yet."

That answer seems to satisfy him, and Theo falls silent as they speed homeward. 

It only takes a few minutes before they're sailing past the support fleet - Gil waggles the wings to acknowledge the hailing lights on the _Hippocampus_ ; her captain is a little scientific and Gil got them to spend an hour going over flying machine plans with him once - and almost in line with the flight lab. The lab is on the port side, two hundred meters back from the bridge, and the doors will open for his radio signal once he's twenty meters out, and this part takes perfect timing. 

"Downdowndowndown -" That's Theo gibbering, of course, everyone's courage has limits. Gil ignores him and keeps steady and level. Ten. Nine. He cuts the engine, so their whirling propellor can play brake. Seven, six, five, four three OPEN one -

The bay windows slam open just in time, and the shock arrestors deploy, and they skid to a stop just shy of the wall.

It's ten seconds before Sleipnir manages a faint, "Wow."

"Wow," Theo echoes, in the louder voice of someone trying to shake off incipient panic. "That was ..."

"Fast," Sleipnir fills in. "That was fast." She pushes herself up, and she's leaping over the side even as Gil retracts the wings. He leans in to check the fuel level while Theo follows her.

When he swings a leg over the side he's amazed to see Theo holding an arm out, like he's inviting a lady to stroll down the Champs-Elysees, smiling like he used to when they were children.

Gil takes his arms, though. No need to overthink it.

"So," Theo says, once his feet are on the floor again. "What are you doing for the rest of tonight?"

Oh, right, it's past midnight. Gil blinks a few times, trying to force his thoughts back from the mechanical intricacies of piloting. "Going to bed?" He should. Sleep is important.

"Want some company?"

"What?"

"We're asking," Sleipnir says, "if you'd like a threesome. Don't look like that. You must have heard of threesomes."

Heard of, yes. Participated in, no. He's never even had a twosome. Er. Gil turns it over in his head. But if there's a reason to turn them down, he can't think of it right now. Theo and Sleipnir are his friends, he wants to trust them, and they're not asking for much. "Alright? If you want?"

"Alright!" Sleipnir pumps her fist in the air, like she's just won something. "Where is your bed, anyway?"

\--

His bed is in a curtained-off alcove just aft of his private lab, because Castle Wulfenbach understood that Sparks sometimes got fits of inspiration in the middle of the night and didn't like to run far to start building, and sometimes kept running after inspiration until far too late and didn't like to stagger far before they fell over. The blankets are approximately straight, and the stack of books beside his bed isn't in more danger than usual of falling over, even when Theo's vest lands right on it. Gil would be annoyed if it weren't for the way his friend is _grinning_ at him. "Ooh, fur? Moving up in the world? No wonder you wouldn't talk to us."

"It came with the lab." He's about ninety percent sure it's Persian mimmoth, actually.[1]

[1] A long-haired variety which, confusingly, has been traced back to Norway. The conspicuous effort of sewing enough hides together for a blanket would make Persian mimmoth fur the height of fashion, if the idea didn't make so many people queasy.

"That's okay, at least it's a big bed," Theo says, as casually as he might comment on a new corkscrew design.

It has to be or he'd roll off it, but that isn't what Theo means and the thought of what he does mean is leaving Gil blushing and nervous again. "Yeah," he mumbles, and if they're getting undressed he probably should too, shouldn't he? Gil fumbles off his vest and tries to yank his shirt over his head. It's not usually difficult, but he somehow gets his arms tangled up while it's halfway over his head, the kind of mess that would knock his glasses off if he wore glasses. He can hear Sleipnir laughing at him. 

Or maybe just laughing, because her hands pull the shirt away and fling it across the room, and she's standing in front of him in her pantaloons and grease-spotted camisole and nothing else and he can almost feel her breath as she says, "Want to try that again? Mine's easier," she informs him, sounding smug. "No sleeves."

Uh. Is this usually what people get up to in bed? Well, before they go to bed? "Okay?" Gil takes hold of the hem and tugs up, and Sleipnir lifts her arms to help, and in a second her braid is thumping against her bare back.

She still has freckles halfway down her chest. Her breasts are bigger than the last time Gil saw them bare, five years ago, and her nipples are red and standing out. That's a good sign, isn't it? "Can I touch you?" he asks her, hoping it doesn't sound too - scientific. 

"Of course." She apparently doesn't want to give him more chances to mess up, because she grabs his wrist and presses it to her chest. Gil gives an experimental squeeze. Ooh, that's nice. "Theo? Get him out of the rest, would you? I don't think he can manage for himself."

"Sure thing," Theo says, and Gil feels arms wrap around him and shove his trousers off his hips. When did Theo lose his shirt? Does sex make everyone stupid or is Gil just unlucky? Theo grabs at his underwear next, and Gil shivers as it slides away. "Gil? You okay?"

"Wonderful." Why did he ask that? 

"Oh, good," Theo says, and shoves him onto the bed. 

It takes them a few attempts to get their limbs sorted out, but they manage it eventually, ending with Gil flat on his back on the blanket and Theo and Sleipnir leaning over him with matching grins. Sleipnir is giggling. "Been a while, has it? Did you run out of girls in Paris?"

"I was busy! I had a lot of classes!" And even the handful of women Sparks hadn't kept up with his ideas the way Miss Clay had so automatically, but bringing that up right now feels churlish, given Sleipnir hasn't even broken through yet. "How can you tell, anyway?"

They exchange a look. It's the kind of look that has a lot more information in it than it has any right to. Then Theo says brightly, "Never mind that, we'll just have to make up for lost time," and runs a hand down Gil's side, right to the ticklish spot just under his ribs. 

It would be nice to say he gives as good as he gets, over the next few minutes, but the truth is that Gil is too busy trying to keep track of what's going on to make more contributions than a few nervous touches. There are hands all over his body, he can't always tell whose, and hands slipping between his legs and making him gasp. Theo throws a leg over his thighs at some point, pinning him to the bed, and Gil curls his toes in the bedspread and clutches at Theo's shoulder. Sleipnir's hair tickles his chest as she licks his nipples, and Gil whimpers, and she asks if he's amenable to kissing. It seems an absurd thing to ask after the liberties they've taken already. He nods. Theo goes in for the kiss. 

There was a time, when Gil was young and awkward and Theo was reliably kind, that Gil daydreamed about kissing Theo. There were fireworks, in his head. There aren't now, he's been kissed by enough girls he wouldn't have expected it, but it's warm and relaxing and he finds himself running his fingers through Theo's hair and frowning when he pulls away. But then Sleipnir moves in, and she kisses harder than Zola did.

Gil's not really sure how, but he ends up on his side, face mashed into Theo's collarbone while Sleipnir hums against his spine and her hand plays over both their hardnesses. He can't stop himself from jerking his hips, and it would be embarrassing to lose control like this if he weren't fairly certain it was the point. Theo's hands are tangled in his hair, and he keeps whispering things like "Just like that," and "Yes," and "You're beautiful," which would make Gil blush if he had any blood left.

He closes his eyes, instead, trying to gather his wits. And failing, because next thing he knows he's in the middle of an orgasm. At least he knows what those feel like. This one's more intense than usual, and leaves him shaking, half-hearted attempt at asking them to slow down dissolved into a wail.

"Hey," Theo is saying, soft into his ear. "You okay? Was that too fast?"

No fair asking a two-part question like that, where the answers go in opposite directions and he can't just nod. "I'm fine," Gil says instead. What goes after that? "Just need a minute. You didn't - Can I?" He takes Theo's distracted mumble for an affirmative and lowers a hand between them to stroke. 

It's easier to focus now, his insistent arousal reduced to background noise. He can pay attention to the soft texture of Theo's skin, the wooly texture of his pubic hair, the musical noise of his moans. He should have turned the light on, to do a proper comparison study. 

Sleipnir's voice puts in, "Don't I get a turn?" 

"Oh - uh - "

"If you're up for it."

"He will be," Theo says. He sounds like he's trying to sound smug, but mostly hitting breathless. "In a minute, though." Right, they're in the middle of something. Gil makes a humming noise he hopes translates as agreement, and tries to look over his shoulder at Sleipnir. She takes the opportunity to lick his ear. 

There's no reason that should feel as good as it does. Gil makes an undignified noise and then a louder one as Theo twitches and comes in his hand. 

"Alright," Theo says, once his breathing has settled. "I think it's the lady's turn now, don't you?"

"Right," Gil says. "Need more data."

Sleipnir sounds like she's laughing as she says, "Oh, so you're just here to experiment?" Before he can come up with an answer she's grabbed his arm and yanked and suddenly he's flat on his back, again, looking up at her grinning with the red braid slipping over her shoulder. He wants to ask if he can take it down and run his fingers through it, but that feels like an imposition, even if Sleipnir is running her fingers some very private places in an attempt to get data on his refractory period. Which is apparently short. Well, good. It might be fun to eat her out but he'd rather lie back and let her set the pace. "Good old three-body problem?"

"Always worth another solution." Theo's propped himself up on one elbow, watching them. 

Gil mock-scowls. " _Another_ solution? How many threesomes have you two had?"

"Only four," Theo informs him. "Don't get jealous."

He was distracted enough by the joking around - it feels so good to joke with them again - that Sleipnir's breath in his ear is a surprise. "So can I substitute the integral?"

"That is the worst euphemism I've ever heard and yes."

Gil's not sure what he expected it to feel like. Warm, his mind supplies not particularly helpfully. His nerves are overstimulated, jangling for attention without any clear reason why. He can feel, very distinctly, Theo's hand guiding him in and Sleipnir's braid tickling his collarbone as she throws her head back and moans. Breathe, he has to breathe. Oh. That's nice. No wonder people like this.

"Here," Theo says, and lifts Gil's hand to press it between Sleipnir's legs. Oh, so that's what a clitoris feels like. He rubs a little, feeling it slip back and forth like a loose toggle button, and Sleipnir moans again, and Theo makes an encouraging noise. Gil keeps going. Sleipnir is almost yelping now, rocking back and forth over his hips and sweat glistening on the curve of her breasts, and Gil presses down with his thumb and she outright screams. The way her body arches makes him think of a cat pouncing on a mimmoth, muscles taut and mind focused.

So that's what an orgasm looks like on a woman. No wonder they're supposed to enjoy them so much. Is he going to - oh. Yes, apparently. It's not as distracting as the first one; he manages to disentangle the hand he wasn't using from his blanket and bury it in Theo's hair.

"Mmmm," Theo says, as Sleipnir disentangles herself. "You don't have to be up early tomorrow, do you?"

Even Gil can work that one out, for all that his head is spinning and he barely feels strong enough to climb under the blanket. "Stay the night," he mumbles. "S'fine."

\--

Gil is woken not by the first rays of sun trickling in from the lab windows and somehow getting past the curtain to the sweaty pile of bodies in his bed, but by an insistent query of, "Tee?"

He's used to waking up fast, and his brain skips from _Tee_ to _Zoing_ to _Worktime_ without bothering to detour to _Pants_ before he shoves the curtain back. It only takes a second after that for his brain to catch up with background information, though, and Gil finds himself blushing and waving his hands. "Uh - "

But Zoing, antennae waving in surprise, has already spotted the other bodies. "Threetee," he declares, and scurries away again.

They have four minutes and twenty seconds, then; it will take that long for Zoing to get to the nearest boiler and back and let it steep properly. Gil spins around, gives Theo and Sleipnir each a shake on the shoulder, and grabs his abandoned clothes.

Four minutes later they're all three looking more or less civilized, even if their hair is sticking up at odd angles. Sleipnir's is at least mostly still in the braid. She looks suspiciously smug, and Gil is sure he's blushing. He stuffs his hands in his pockets and looks out into the lab. "Er." Wonderful start. "About last night. Late last night, that is."

"Want to do it again sometime?" There's not a hint of a smirk on Theo's face; his smile is so warm it hurts. 

"If you want to." Dammit, that makes it sound like he didn't enjoy himself. Why can't he be articulate around women even when he has no romantic interest in them whatsoever? "Er. Can it just be our secret, though? I mean, my father knows everything and he's probably going to scream at me for - You're using Maiden's Weed, right?" He should have asked last night. "I just don't want the whole school to know."

Sleipnir rolls her eyes. "You should have asked about the Maiden's Weed last night. Did you just go for it with your girlfriends in Paris?"

"I didn't _have_ girlfriends in Paris!" 

He hadn't meant to admit to that but the words got out before he could stop them. Side by side on the edge of the bed Sleipnir and Theo are wearing identical expressions of crogglement. Dammit, why isn't Zoing back yet? Gil swallows and pushes on. "There were some girls who wanted to be but none of them were Sparks. They were nice but, well. Not for me."

Sleipnir sounds a little strangled as she says, "So that was the first - "

" _Yes._ Can we change the subject now?"

It shouldn't feel as strange as it does when Theo surges up and enfolds him in a hug. "You did fine," he whispers into Gil's ear, and Gil relaxes a little. Theo pulls back to grin at him. "Now. On to the important things. Can we try out your flying machine again? Because that was _amazing._ "

Finally, a technical question. "Give me a few days," he says. "The engine improvements were just some quick stuff Miss Clay came up with but I'm sure if I do a proper overhaul -"

"Tee!"

Zoing is holding up the tray like a trophy. A steaming teapot and four cups and, oh, he's _amazing_ , he brought _scones_. Where did he get those in six minutes? "Thankyu," Gil mumbles around his first mouthful.

Theo snatches up one of the cups. "So what were we working on all night? If anyone asks? Flying machine?"

"Exactly." Lucky Theo understands the importance of a cover story. Gil crouches down to go eye-to-eye with Zoing, who's carefully maneuvering his teacup with one claw to drink it without actually pulling his collar back. "Zoing, I'm going to be very busy today," he says. "But I'm supposed to inspect Dr. Pfennilhaus's new autoacidulator with my father at noon. Can you remind me at eleven-thirty so I have time to wash up first?"

"Ontim," Zoing assures him, and pushes Gil's teacup closer. "Drinkup."

It's refreshing to have someone around with such simple priorities. Gil takes a drink.

Sleipnir puts in, "Autoacidulator? Did he actually get it working this time?"

She must have seen the Version Alpha back in December. And Beta in February. Gil would feel jealous - he's only read the reports - except, well, there's a reason she asked. "I'll tell you all about it if this one explodes too," he promises. 

"Bim?" Zoing's antennae start to wave, the way they always do when he's nervous. Gil suppresses the urge to scratch behind them; it's not safe this close to a moult.

"Don't worry," he says instead. "The lab has a bicarbonate spray system."

"Sqirpl."

Theo, who knows better than to be nervous on Gil's behalf about a few explosions, claps him on the shoulder. "Come by after dinner," he suggests. "Tell us some more stories. Maybe Miss Clay will be there this time."

"You'd like that, wouldn't you?" Sleipnir is grinning the grin of someone who finally has empirical proof that Gil likes women.

He would like that. He desperately wants to get to know Miss Clay better. But as wonderful as it is to have someone around who can improve his engine designs after she's barely studied them, it's not the idea of romance that's driving him. It's the mystery.

Should he bring them in on it? If there's anyone he can trust with the possibility of a secret Spark, the question of what Doctor Beetle was so desperate to hide, it should be his old friends who -

\- have been living on Castle Wulfenbach, under his father's guiding hand, all this time. Who he's only been speaking to again since yesterday afternoon. 

Gil can't trust anyone, except Zoing, and Zoing can't help him. He should be used to that by now.

"You can shut up," he says, and it's easy to blush and glower. "She has a lover already, remember? That new spark. Zinzer." 

Sleipnir rolls her eyes. "Well, come by anyway. Maybe you can charm her away. I mean, you're pretty cute when you don't have your foot in your mouth."

"Good to know you're on my side here."

"Of course we are," Theo says, and raises his teacup like he's making a toast. "That's what friends are for."

\--

**Author's Note:**

> Thanks to atagotiak and phoenixyfriend for looking this over!


End file.
